View transmission system



Dec. 26, 1933. H. H. BATES VIEW TRANSMISSION SYSTEM Filed April 18, 1950 2 Sheets-Sheet l 1" I 4 a Hmpl/f/er Fedmy A #2 5 /4502; fluxl'llary Shunt Field Fansml'ffer INVENTOR Ha rryEBafes ATTORNEY Dec. 26, 1933. H. H. BATES VIEW TRANSMISSION SYSTEM 2 Sheets-Sheet 2 Filed 'April 18 1930 a mm m T /R N O E y /4W N r .A l r Patented Dec. 26, 1933 PATENT OFFICE VIEW TRANSMISSION SYSTEM Harry H. Bates, Ridley Park, Pa., assignor to Westinghouse Electric & Manufacturing Company, a corporation of Pennsylvania Application April 18, 1930. Serial No. 445,315

6 Claims.

My invention relates to view-transmission systems and it has particular relation to systems wherein the scanning operations, at the sending and the receiving stations, are accomplished by devices such as rotating discs, oscillating mirrors and the like.

In view-transmission systems, of the type wherein the scanning operation is performed by a rotating disc provided with a plurality of cir- 10 cumferential, spirally disposed perforations, it is essential that the sending and receiving discs 7 shall be continually maintained in motional synchronism, as well as in unvarying phase relationship. If the angular velocity of the receiving disc changes from that of the transmitting disc,

the received view will appear to move rapidly toward the one or the other side, depending upon which of the discs is speeding up; if the velocity of both discs is the same but the .phase relationship between them is incorrect the receivedyiew will be too high or too low in the viewing aperture.

It is a comparatively simple matter to adjust the phase-relationship between the two discs since the motor driving the receiving disc may momentarily be accelerated or decelerated until the received view is in frame.

On the other hand, it is difiicult to keep the angular velocities of thetransmitting and receiving discs constant and equal, after framing has once been accomplished, by manual control.

It is, accordingly, an object of my invention to provide improved synchronizing means for viewtransmission systems.

Another object of my invention is to provide,

in a view transmission system, means for automatically maintaining synchronism between a transmitting scanning device and a receiving scanning device.

A still further, and more specific, object of my invention is to provide means whereby synchronizing impulses may be sent, between a transmitting and a receiving station, on the same carrier-wave that is utilized for the transmission 5 of the frequencies representing a view.

In a preferred embodiment of my invention, the aforesaid objects, and others appurtenant thereto, are achieved by driving a transmitting scan"- ning device at a constant speed, deriving. therefrom a series of impulses and utilizing the said impulses, at a receiving station, to control the speed of a prime-mover that drives a receiving scanning device.

Specifically, I provide a transmitting scanningdisc with an auxiliary circumferential series of openings, each opening being so spaced with respect to the main scanning openings that the transmitting photo-cell receives light through the said auxiliary openings only during the intervals when it is not receiving light from the view through the main openings.

The output current from the photo-cell, therefore, includes a component having a frequency determined by the angular velocity of the scanning disc and the number of auxiliary openings. The said component appears, independently of the view-frequencies, in the receiving device and is, thereat, utilized to control the speed of the motor that drives the receiving scanning-disc.

The novel features that I consider characteristic of my invention are set forth with particularity in the appended claims. The invention itself, however, both as to its organization and its method of operation, together with additional objects and. advantages thereof, will best be understood from the followin description of a specific embodiment, when read in connection with the accompanying drawings, in which:

Figure 1 is a diagrammatic view, partly in section, of a view-transmitting station comprising a preferred embodiment of my invention;

Fig. 2 is a diagrammatic view, partly in section, of a view-receiving station,

Fig. 3 is a sectional view of a transmitting device, taken along a line corresponding to the line .III-HI of Fig. 1; I

Fig. 4.. is a sectional view of a receiving device, taken along a line corresponding to the line IV-IV in Fig. 2;

Fig. 5 is a fragmentary view of a receiving scanning-disc, illustrating the relative position it assumes with respect to fixed portions of the apparatus when correctly synchronized;

Fig. 6 is a diagram to which reference will be made in connection with the description of the operation of my improved system; and

Fig. 7 is a view, in elevation, of a scanning disc, constructed according to my invention, drawn substantially to scale.

The view-transmitting apparatus' shown in Figs. 1 and 3 of the drawings includes a scanning disc 1 through which extend a plurality of scan-' ning openings 3, disposed in a spiral, and a plurality of auxiliary openings 5 that are circularly disposed. The disc is rotated by--a constant-- speed motor 7' that is supplied with current from any convenient source (not shown).

A housing 9, in whichare disposed a photoelectric cell 11 and a small mirror 13, is mounted. rearwardly of the scanning disc. The front wall of the housing, through which extend a small opening 15 and an opening 1'7 that defines the field of view, lies in a plane parallel to the plane of the disc and closely adjacent thereto.

The small opening 15 in the front wall of the housing registers with the auxiliary openings 5 in the scanning disc. The view-defining opening is slightly longer than the radial distance between the remote margins of the first and last openings in the scanningspiral and its width is less than the angle subtended between any two successive openings in the said scanning spiral.

An amplifierand radio-transmitter, indicated on the drawings by a rectangle 19 is so disposed as to be controlled by the output current from the photoelectric cell.

A light-source-21, of relatively high intrinsic brilliancy, is enclosed within a small housing 23 mounted upon the main housing. The bottom' wall of the light-housing is provided with a slot into which a minor peripheral portion of the scanning-disc, suflicient to include the auxiliary openings 5, projects. The said scanning-disc, therefore, when it is rotated to bring the auxiliary openings into and out of register with the opening in the front wall of the photoelectric-cell housing, causes a series'of light impulses to strike the mirror 13 from which they are reflected upon the photoelectric-cell to periodically alter the amplitude of the output current therefrom.

When the dimensions of the view-defining window are properly chosen with respect to the angular spacing of the scanning-openings, and when the size and relative positioning of the auxiliary openings 5 are correct, the auxiliary openings and the opening 15 in the photoelectriccell housing cannot register during the intervals when a scanning opening 3 is traversing the window 17. The dimensions of the view-defining window, and the relation of the main scanningopenings to the auxiliary openings are clearly shown in Fig. '7 of the drawings.

The receiving apparatus, illustrated diagrammatically in Figs. 2 and 4 of the drawings, comprises a motor 25, to the shaft of which is afiixed a scanning-disc 27 similar to the scanning-disc 1 included in the transmitting apparatus. The receiving disc is provided with a spirally disposed series of main scanning openings 29 and a circularly disposed series of auxiliary, or synchronizing openings 31. I

A glow-tube 33 is supported rearwardly of the scanning-disc, within a housing 35 the front wall of which lies in a plane parallel to the plane of the disc and closely adjacent thereto. The front wall of the housing is provided with a view-defining opening 37, clearly shown in Fig. 4, through which light from the glow-tube is permitted to pass as the main scanning-openings move before the said tube. A lens 39 may be mounted in front of the view-defining opening to enlarge the view, if desirable.

A view-frequency receiver and amplifier 41; of any conventional type, is provided to energize the glow-tube, the input terminals of the amplifier being connected to an energy-collecting device 43.

A photoelectric-cell 45 is mounted within a small housing 4'7, disposed forwardly of the disc 27, the output terminals of the tube being connected to an amplifier 49 which energizes an auxiliary field winding (not shown) of the motor 25.

An opening 51 extends through the wall of the photoelectric-cell housing nearest the disc, the opening being so disposed as to register with the auxiliary openings in the scanning disc as the latter rotates.

In the operation of my improved view-transmission system, the synchronizing openings 5 in the transmitting scanning disc register with the openings in the lamp housing 23 only during the intervals between the passage of successive scanning openings 3 across the view-defining window 1'7. The output current from the photoelectric-cell, therefore, in addition to being modulated by the light from the view, is also modulated by the periodic light pulses permitted to fall upon the cell by the synchronizing openings, and the said modulations subsequently appear as variations in the amplitude or frequency of the radio carrier-wave.

At the receiving station, the incoming carrier-wave is demodulated, and the view and synchronizing-frequencies derived therefrom are impressed across the terminals of the glow-tube 33, giving rise to variations in the luminosity thereof. By reason of the fact, however, that the synchronizing impulses, at the transmitter, are introduced into the carrier wave only when the scanning openings are out of register with the view-defining window 17, they may be utilized, at the receiver, for synchronizing purposes without interfering with the reception of the view-frequencies.

To be effective for synchronizing the receiver, means must be provided whereby the intermittent light from the glow-tube, responsive to the synchronizing impulses. shall function to cause instantaneous acceleration or deceleration of the scanning disc. To accomplish this purpose, the opening 51 in the photoelectric-cell housing 47 is so disposed with respect to the path of travel of the auxiliary openings in the scanning-disc that, when the receiving and scanning discs are in synchronism, registry of the auxiliary openings in the transmitting disc with the openings in the light-housing 23 is represented by partial registry of the analogous openings at the receiver. The instantaneous condition of the receiving disc representing synchronism is clearly indicated in Fig.

5 of the drawings.

If, therefore, the receiving disc is out of synchronism with the transmitting disc, either more or less li'ght, occasioned by the synchronizing impulses, will be received by the photoelectric-cell 45 from the glow-tube.

Assuming that the receiving disc is rotating in the direction of the arrow in Fig. 5, if it leads the transmitting disc, the photoelectric-cell receives more light than normal; if it lags behind the transmitting disc, less light than normal falls upon the cell.

By properly connecting the output terminals of the amplifier 49 to the auxiliary winding (not shown) of the driving motor 25, whereby the field strength is diminished when the disc lags and is increased when it leads the transmitting disc, the tendency to lag or lead is thus automatically met and compensated.

The use of stroboscopes for disc-speedadjustment, however, is not necessary, since the incoming synchronizing impulses may be, themselves, utilized for this purpose. Assume, for example, that the transmitter is in operation and that it is desired to bring the receiving disc into synchronism with the transmitting disc. In-such event, after the receiver is placed in operation, the light-effects exemplified by Fig. 6 will be apparent in the view-receiving window;

1. If the speeds are the same. but the scanning but differ slightly in phase relation, the received view is cut short at the top or the bottom thereof.

By proper adjustment of a receiver-motor fieldrheostat (not shown). therefore, o'r 16y the actuation of a framing device such as is disclosed in the Ramsey Patent No. 1,602,121, the receiving operator, through observation of the phenomena enumerated above, can manually bring the receiving disc into exact synchronism, both as to speed and phase relation, with the transmitting disc, after which it is automatically so maintained. a

It also lies within the scope of my invention, instead of employing a single small opening in the photoelectric-cell housing at the receiver, to utilize, in lieu thereof, an elongated opening wherein is disposed a screen that varies evenly in translucency along its length. Lack of synchronism, therefore, would be represented by increase or decrease of the light admitted to the photoelectric-cell in substantially the same manner as in the case of the small opening.

It will, accordingly, be apparent that my improved view-transmission system is substantially automatic in operation and that synchronism, having. once been secured, is thereafter maintained without further attention on the part of the operator of the receiver.

I also wish to particularly point out that my invention is not restricted to use in connection with scanning devices of the disc type, but that it may be practiced in connection with movable scanning devices of any desired configuration, such as belts, mirrors and thelike.

Although I have illustrated a single specific embodiment of my invention, many modifications thereof will be apparent to those skilled in the art to which it pertains. My invention, therefore, is not to be restricted except insofar as is necessitated by the prior art or by the spirit of the appended claims.

I claim as my invention: I

1. In television apparatus, the combination of a transmitter including means for transforming light energy into electrical energy, a scanning element having a plurality of series of light d1 recting means, one of said series for controlling the passage of light from an object or picture to said energy transforming means, another of said series of light directing means for controlling the passage of light to said energy transforming means when light from the object or picture is cut off, a motor for operating the scanning element, a light source, and means for transmitting energy in accordance with that transformed from light; and a receiver including a seaming element, a variable-speed motor for operating the scanning element, means for transforming received electrical energy into light the intensity of which is dependent ,upon the strength of the received energy means for transforming light into electric energy, said last-named scanning element having means for directing light due to energy controlled by said first light source upon the lastnamed transforming means, and means for controlling the speed of the last-named motor in accordance with the electric energy coming from the last-named transforming means.

2. In television apparatus, the combinationof a transmitter including a scanning'element having scanning openings arranged to pass over a view field, means for transforming light coming from an object into electric energy, a light source, said scanning element having synchronizing openings so spaced relatively to the scanning openings as to permit the passage of light from said source to the transforming means when the scanning openings are out of the fieldof view,

a receiver including a scanning element having scanning openings arranged to pass over a field of view, means for converting received electrical energy into light, means for transforming light into electrical energy, said receiver-scanning element having synchronizing openings therein so spaced relatively to the scanning openings as to permit the passage of light from the converting, means to the second transforming means when the receiver-scanning openings are out of the field of view, a motor for driving the receiverscanningelement, and means responsive to electrical energy coming from the second transforming means for controlling the speed of the motor; and means for transmitting energy from the' transmitter to the receiver in accordance with the output energy of the transmitter-transforming means.

3. In television apparatus, the combination of a transmitter having a view field, a scanning element having scanning openings for passage over 9 the view field, means for converting light passing through the scanning openings when the latter pass over the view field into transmissible energy the strength of which varies with the intensity of the light, a light source, said scanning element having synchronizing openings which are so spaced relatively to the scanning openings as to I provide for the passage of light from said source to the converting means after a scanning opening has left the field of view and before the next succeeding scanning opening reaches the field of view; a receiver having means for transforming the transmissible energy into light the intensity of which varies with the strength of such energy,

a view screen, a scanning element having scan:

ning openings through which light passes from the light-output transforming means to the screen; said receiver scanning means having synchronizing openings so spaced relatively to the scanning openings as to provide for the passage of light from the light-output transforming means after ascanning opening leaves the screen.

the transmitter and the reception thereof by the receiver. v

4. In television apparatus, the combination of a transmitter including means providing a chamber, first transformation means for transforming light energy into electrical energy and arranged in the chamber, a scanning disc arranged adjacent to a wall of the chamber and covering awindow formed in the wall, the disc having scanning openings disposed to pass over the window, a source of light, said wall having an opening therein for passing light from the source to the transformation means and said scanning disc being arranged to cover said last opening and having openings therein arranged to successively register with said opening during the intervals after a scanning-disc opening leaves the window and before the next scanning-disc opening reaches the window; a receiver providing a chamber, asecond transformation means in the chamber for transforming received electrical energy into light, said chamber having a wall provided witha .view screen and with an opening, a scanning disc extending into the chamber and disposed closely adjacent to said wall and covering said screen and opening, said scanning disc having scanning openings therein to cross the screen and having synchronizing openings so spaced relatively to the scanning openings that they register with said receiver-wall opening during intervals after a scanning opening leaves the screen and before the next scanning opening reaches the screen, a third transformation means for transforming light passing through the registering receiving scanning-disc synchronizing and wall openings into electrical energy, a motor for operating the receiver scanningdisc, and means'for. controlling the speed of said motor including means responsive to the output energy of said third transformation energy from the transmitter. and the reception thereof by the receiver.

5. In a view-transmission system, a transmitting station including a scanning device, a receiving station including a scanning device, means activated by the transmitting scanning device for deriving synchronizing electric impulses intermediate successive groups of electric impulses representing a view to be transmitted, a light source at the receiving station so disposed as to be controlled by said impulses, a photo-electric-cell, means whereby a partially obstructed path is periodically established between said light source and said photoelectric-cell when said scanning devices are in synchronism, and means responsive to said photoelectric-cell for controlling the movement of said receiving scanning device, whereby a tendency toward an increase in the light-conveying capability of said path is compensated by deceleration of said receiving scanning device, and a tendency toward a decrease in the light conveying capability of said path is compensated by acceleration of said receiving scanning device.

6. Apparatus for the production of impulses for synchronizing purposes and impulses representative of the characteristics of elemental areas of a subject tobe scanned, saidapparatus comprising scanning means of the disc type having a plurality of ray-directing means disposed in at least two groups around said disc, one of said groups being adapted to scan a subject to be televised, the other of said groups being caused to traverse a ray of uniform intensity, a device disposed in the path of and responsive to the rays directed by said groups of ray directing means, and means for causing said device to be affected alternately by the rays from each group of ray directing means. HARRY H. BATES. 

